What happens when things collide

Science · Energy · ages 9-10

Name ______________________ Date ____________

Two balls collide. Where did the energy that starts moving the second ball come from?
- It came from nowhere new
- From the first ball, the one that was moving
- It was already stored inside the second ball
A moving ball hits a ball that is standing still. What usually happens to the still ball?
- It speeds up and starts moving
- It stays perfectly still
- It bounces back and forth forever without slowing down
When two objects collide, energy can transfer from one object to the other.
Circle one: True False
Two toy cars crash together. Besides a change in speed, what else might you notice?
- A sound
- Nothing else happens
- The cars must stick together
A big heavy ball rolls slowly toward a small light ball that is standing still. What is most likely to happen when they collide?
- The small ball barely moves at all
- The big ball speeds up instead
- The small ball speeds off quickly
Before the crash, Ball A's speed was 8. After the crash, Ball A's speed was 2. How much speed did Ball A lose?
Answer: ______________
A fast small ball and a slow big ball roll toward each other and collide head-on. What is most likely?
- Only the small ball changes speed
- Only the big ball changes speed
- Both balls change speed and direction, depending on how fast and how big each one is
Ali says: 'When my toy car hits a wall, the energy just disappears.' What is wrong with what Ali said?
- Ali is right, the energy disappears completely
- Energy does not disappear, it turns into sound and heat
- The wall gains all the speed instead

Answer key

For grown-ups. Fold this page away before handing over the rest.

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From the first ball, the one that was moving · Energy doesn't appear out of nowhere. It transfers from the moving ball into the one it hits.
It speeds up and starts moving · The moving ball passes some of its energy to the still ball, so the still ball starts moving too.
True · That's exactly what happens in a collision: energy moves from one object into the other.
A sound · Collisions often make a sound. Some of the energy turns into sound instead of staying as motion.
The small ball speeds off quickly · Even a slow, heavy ball carries energy. That energy pushes the light ball, which speeds up fast because it is light.
6 · 8 minus 2 is 6. That's the speed Ball A gave up, and it's the same amount Ball B gained.
Both balls change speed and direction, depending on how fast and how big each one is · Predicting a collision means looking at both speed and size together for both objects, not just one part.
Energy does not disappear, it turns into sound and heat · Energy can't just vanish. In a crash into a wall, it moves into sound, heat, and small vibrations instead.